Taste is significantly involved in the regulation of food intake and in the etiology and treatment of nutrition-related disorders. Thus information about taste physiology is relevant to the maintenance of health and well-being. This proposal is for research directed at elucidation of taste receptor cell membrane mechanisms for the transduction and identification of a taste stimulus. Plant compounds which alter the perception of a taste stimulus can be useful tools for studies of transduction and stimulus identification. In particular, analyses of similarities and differences in the physiological actions and physical and chemical properties of various taste-altering compounds could reveal taste-altering mechanisms and thus elucidate physiological taste mechanisms. The blowfly Phornia regina can be a useful, relatively simple model system for such physiological studies. The actions of two groups of plant compounds which selectively suppress sweetness perception in humans, the gymnemic acids (from Gynnena sylvestre) and ziziphins (from Ziziphus jujuba), have been studied in fly taste receptor cells. Recently, Hovenia dulcis has been found to contain a taste-altering principle, "hodulcin," which also selectively suppresses sweetness perception in humans. This proposal is to study the effects of hodulcin on fly behavioral and receptor cell action potential responses to sucrose and NaCl stimuli. The experiments are designed to 1) determine the appropriateness of the blowfly as a model biological system for studies with hodulcin and 2) determine concentration-effect and time course relationships for the actions of hodulcin on fly receptor cells. The data will permit comparisons of similarities and differences of the effects of hodulcin with effects of gymnemic acids and ziziphins measured in previous experiments and will provide basic information necessary for future comparative studies with compounds from the three taste-altering plants.